Gas lift is a commonly used method for producing wells which are not self flowing. Gas lift consists of initiating or stimulating well flow by injecting gas at some point below the fluid level in the well. When gas is injected into the formation fluid column, the weight of the column above the point of injection is reduced as a result of the space occupied by the relatively low density gas. This lightening of the fluid column is sufficient in some wells to permit the formation pressure to initiate flow up the production tubing to the surface. Gas injection is also utilized to increase the flow from wells that will flow naturally but will not produce the desired amount by natural flow.
In gas lift operations, the well may be produced through either the casing or the production tubing. If the well is produced through the casing, the lift gas is conducted through a tubing string to the point of injection, and if the well is produced through production tubing, the lift gas is conducted to the point of injection through the casing annulus or through an auxiliary tubing string.